Min Post-mortem Research Articles

Genetic Association and Expression of JHDM1A Gene Related to Meat pH in Commercial Pigs

An experiment was conducted to study the association and expression of JHDM1A gene as a candidate gene for meat quality. The polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using restriction enzyme on a total of 300 muscle samples of [Duroc × (Large White × Landrace)] pigs. Results showed that JHDM1A gene was significantly associated with meat pH 45 min post-mortem (p.m.) (p<0.05). Allele frequencies for G and C were 0.53 and 0.47. The genotype frequencies for GG, GC, and CC were 0.24, 0.58, and 0.18, respectively. The Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) study were analyzed between low and high pH 45 min p.m. groups (n=10 per group) according to the association result. JHDM1A expression was higher in animals with a low post-mortem meat pH 45 min (p<0.05). Therefore, polymorphism and expression in the porcine JHDM1A gene might be the important candidate genes to improve meat quality traits in terms of meat pH.

Associations of Apoptotic and Anti-Apoptotic Factors with Beef Quality, Histochemical Characteristics, and Palatability of Hanwoo Longissimus thoracis Muscle.

Simple SummaryAfter the onset of muscle fiber apoptosis, various apoptotic and anti-apoptotic factors are selectively increased. These factors are directly and/or indirectly associated with tenderness variation. Given the complex relationship between the apoptosis-related molecules, more data are needed on how the expression patterns of these factors during the post-mortem period affects the palatability of beef. In this study, the combination of expression levels of apoptotic (cytochrome c and caspases) and anti-apoptotic (small heat shock proteins) factors at 45 min post-mortem tended to be associated with Warner-Bratzler shear force and tenderness attributes in Hanwoo steers with a lower degree of marbling. Meanwhile, levels of these molecules at 24 h had a somewhat limited effect on the beef tenderness. Clearly, these results demonstrate that expression levels of apoptotic and anti-apoptotic molecules at the early post-mortem period may be a relevant indicator to explain the tenderness variation in Hanwoo.This study compared the meat quality, histochemical traits, palatability, and expression levels of apoptotic (cytochrome c and caspases) and anti-apoptotic (small heat shock proteins) factors at 45 min and 24 h post-mortem of Hanwoo Longissimus thoracis muscles in groups categorized by Warner-Bratzler shear force (WBS) values to investigate the association between beef tenderness variation and apoptosis-related molecules. There were no differences in marbling scores, meat quality traits, or histochemical characteristics among the WBS groups (p > 0.05) indicating no significant effect on the tenderness variation in the current study. On the other hand, the low group exhibited higher levels of apoptotic and anti-apoptotic factors (except for αβ-crystallin) at 45 min post-mortem compared to the high WBS group, resulting in higher scores of tenderness attributes (p < 0.05). However, the level of αβ-crystallin at 45 min post-mortem was lower in the low and medium WBS groups compared to the high WBS group (p < 0.0106). At 24 h post-mortem, no significant differences were observed in the expression levels of apoptosis-related factors among the WBS groups (p > 0.05) except for heat shock protein 27 (p < 0.05).

Research Note: Texture characteristics of wooden breast fillets deboned at different postmortem times

The study aimed to understand whether deboning time contributes to the altered texture attributes of wooden breast (WB) fillets. To this purpose, 30 unaffected (NORM) and 30 severely affected (WB) carcasses were selected at 15 min postmortem (PM) and allotted into treatments with different deboning times: A (5 NORM + 5 WB; right fillets deboned at 15 min PM), B (5 NORM + 5 WB; right fillets deboned at 3 h PM), and C (5 NORM + 5 WB; right fillets deboned at 6 h PM). Left fillets from each carcass were deboned at 24 h PM. Multiple instrumental texture analyses were performed on the cranial-middle portion of the Pectoralis major muscles. Irrespective of deboning time, all fillets were subjected to a single 30% compression in the raw state at 24 h PM. All fillets were cooked at 24 h PM and subjected to shear force assessments at 48 h PM using blunt Meullenet-Owens razor shear, Meullenet-Owens razor shear, and Warner-Bratzler shear force. Using an ANOVA mixed model, deboning time was evaluated as a fixed effect within muscle condition (sampling session and carcass ID as random effects). Compression force assessment of raw meat at 24 h PM showed that WB fillets exhibited the greatest hardness when they were deboned at 6 h PM (15 min = 35.4 N; 3 h = 30.9 N; 6 h = 48.0 N; 24 h = 30.6 N; P < 0.05). Differently, deboning time had no effect (P > 0.05) on raw compression force values in NORM fillets. In cooked NORM fillets, shear force values were the greatest in fillets deboned at 15 min, and shear force gradually declined with deboning time through 24 h PM. On the contrary, no changes (P > 0.05) in shear values due to different deboning times were observed in cooked WB meat regardless of shear method. These results suggest that early PM changes in breast muscles and their influence on meat texture are different between normal and WB fillets.

Timing and duration of low voltage electrical stimulation on selected meat quality characteristics of light and heavy cattle carcasses

Context The present study investigated the effects of several electrical-stimulation parameters with conventional chilling of heavy- and light-grade carcasses from commercial feedlot cattle on selected meat-quality attributes. Aims The aim was to determine the combination of electrical-stimulation parameters that produced the most desirable results in terms of meat quality, which will serve as a guide to processors seeking to enact best processes in the meat industry. Methods Low-voltage electrical stimulation (110 V peak, 17 pulses/s, 5-ms pulse width) was applied either early post-mortem (PM) at 7 min or late PM at 45 min, for either 30 or 60 s on steer carcasses (n = 98) divided into two weight categories (light (≤260 kg) and heavy (≥290 kg) grades). The Longissimus lumborum muscle was evaluated for sarcomere length, myofibril fragment length (MFL), calpain-1, calpastatin, shear force and drip loss (3 and 14 days PM). Key results There were no significant differences in sarcomere length and no sarcomere shortening was observed. There were minor inconsistencies where early stimulation coincided with marginally longer MFL at 3 and 14 days PM, while late stimulation produced the shortest MFL at 14 days PM. Higher decline in calpain-1 concentration (mean 36.2%) was recorded in the early stimulated carcasses compared with the late stimulated carcasses (mean 29.7%) from 1 to 24 h PM, while calpastatin concentration decreased at a similar rate (mean 24%). Early stimulation resulted in lower shear force (P &amp;lt; 0.05) at 3 days PM, especially in the heavier carcasses, indicating that higher initial temperature did accelerate tenderisation. At 14 days PM, there were no significant differences in shear force as regards stimulation time or carcass weight. Higher drip loss was however recorded in the early stimulated carcasses. Conclusions Early application of low-voltage electrical stimulation produced faster tenderisation early PM, due to higher rigor temperature, but, after aging for 14 days, all meat was acceptably tender with a lower variability, regardless of the stimulation time and carcass weight. Higher drip loss was associated with higher tenderness, which is normal and not a defect. Implications The use of low-voltage electrical stimulation should be encouraged for its ability to reduce variability in meat quality due to carcass-weight differences, especially in the current feedlot systems.

Collapse of the endogenous antioxidant enzymes in post-mortem broiler thigh muscles triggers oxidative stress and impairs water-holding capacity.

This study was conducted to investigate the effect of the collapse of the endogenous antioxidant enzymes, namely, catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in post-mortem (PM) chicken thigh muscles on the extent of lipid and protein oxidation and the functionality of the muscle in terms of water-holding. To fulfil this objective, the samples were divided into two treatments: one group of muscles (n = 8) was subjected to delay cooling (DC) (at ~ 37°C for 200min PM) and then stored at 4°C for 24h. The second group (n = 8) was subjected to a normal cooling (NC): samples were immediately chilled at 4°C for 24h. DC samples presented a decrease in 16% of CAT, 25% GSH-Px and 20% SOD activity in relation to NC. Consistently, an increase of 36% of total carbonyl, 15% of Schiff bases and 27% of TBA-RS and 14% of tryptophan depletion was observed in DC samples, as compared to NC. The results suggested that DC challenged muscles to struggle against oxidative reactions, consuming endogenous antioxidant defenses and causing protein and lipid oxidation which in turn affect the quality and safety of chicken meat. These results emphasize the role of PM oxidative stress on chicken quality and safety. Antioxidant strategies like fast cooling may be combined with others (dietary antioxidants) to preserve chicken quality against oxidative stress.

Influence of carcass weight on meat quality of commercial feedlot steers with similar feedlot, slaughter and post-mortem management

The effects of beef carcass weight on muscle pH/temperature profile and selected meat quality attributes were evaluated. Twenty-six carcasses from light (≤260kg, n=15) and heavy (≥290kg, n=11) feedlot steers were randomly allocated and stimulated with low voltage electrical stimulation (LVES) for 30s at 7min post-mortem (pm). Quality evaluations were carried out on samples from the Longissimus et lumborum (LL) muscle from the left side of each carcass. Heavier carcasses showed faster pH decline and slower (P<0.05) temperature decline at 45min, 3, 6, 12 and 24h pm. Heavier carcasses passed through the heat shortening window (i.e. at pH6, temperature was >35°C) but there was no sign of sarcomere shortening in any carcass. Significantly lower (P<0.05) shear force values were recorded in the heavier carcasses at 3days pm but at 14days pm, heavier carcasses had numerically lower but not significantly different shear force. Heavier carcasses produced numerically higher but not significant (P>0.05) drip loss at 3 and 14days pm as well as higher L* (meat lightness) (P<0.05) and C* (chroma) (P<0.05) values early (2days) pm. However, at 14days pm, there were no significant differences between the light and heavy carcasses in terms of L* and C*. No significant difference was observed between heavy and light carcasses in terms of H* at 2 and 14days pm. The study showed that heavier carcasses which favor slaughter house pricing can be produced and processed alongside lighter carcasses without significant detrimental effects on meat quality by using low voltage electrical stimulation (LVES).

Effects of postmortem temperature on the physicochemical characteristics of prerigor Pekin duck breast muscles

The effects of postmortem (PM) temperature on prerigor Pekin duck breast muscle quality were assessed. Breast meat was obtained from 90 ducks within 15 min PM and then divided into 3 storage temperature groups at 0, 15, and 30°C for 24 h PM. Results revealed that the meat stored at 0°C had a higher pH value than that stored at 30°C. The R-value tended to increase between 15 min, 2 h, and 24h PM, whereas the water-holding capacity decreased significantly (P < 0.05) with increasing storage time. The drip loss of treatment in meat stored at 30°C was higher than in those stored at 0 and 15°C. As storage periods increased, cooking loss of meat stored at each temperature increased significantly (P < 0.05) at 2 h, but storage temperature does not affect cooking loss of duck breast muscle. The shear force of breast meat at 24 h PM had the lowest value, but meat stored at 30°C increased at 2 h and decreased at 24 h PM. Meat stored at 15°C showed a longer sarcomere length than meat stored at 0 and 30°C. The rate of muscle shortening was high during the 2 h PM for meat at the 3 temperatures. It is concluded that the different temperatures in the range of 0 to 30°C affected the muscle shortening or meat quality of the duck breast meat.

Pre-slaughter handling and pork quality

Environmental variables, as sound levels, were collected during the pre-slaughter process in 18 different Belgian commercial slaughterhouses. Four pre-slaughter phases were determined: firstly after arrival of the truck at the slaughterhouse and just before unloading, secondly during unloading, thirdly at lairage and finally while moving to the stunner. A total of 8508 pigs was examined during the pre-slaughter process, of which the pHLT (M. longissimus thoracis), at 30min post-mortem was measured. For each pre-slaughter phase, variables which might influence pork quality were determined. Moreover, this study made it possible to infer a checklist to represent and predict PSE traits of pork for all kind of pre-slaughter situations. The checklist shows also that the impact on pork quality is more decisive for the variables measured close to the stunning phase. Hence, this information is useful for the industry to optimize handling of pigs, reducing the risk for PSE traits.

Comparison of Physicochemical Characteristics of Hot-boned Chicken Breast and Leg Muscles during Storage at 20℃

The aim of this study was to compare the physicochemical changes of hot-boned chicken breast and leg muscles. Chicken breast and leg muscles from 56 broilers were excised within a 15 min post-mortem (PM) and stored at 20 C. Physicochemical traits were determined at 0.5, 6, 12, and 24 h PM. The ultimate pH of leg muscle was higher than that of breast muscle (p<0.05). The content of glycogen in the breast muscle was relatively higher than that in the leg muscle until 6 h PM (p<0.05). R-values showing rigor mortis of breast and leg muscles were completed after or before 6 h PM. Breast muscle had less cooking loss than leg muscle (p<0.05). Drip loss did not significantly differ between breast and leg muscles with the exception of that at 6 h PM. The sarcomere length of leg muscle was relatively longer than that of breast muscle (p<0.05). The MFI of leg muscle was significantly lower than that of breast muscle (p<0.05). The shear force of leg muscle was lower than that of breast muscle at 6 and 12 h PM (p<0.05); however, that of both muscles did not significantly differ at 24 h PM.

The effect of hot-boning and reduced added phosphate on the processing and sensory properties of cured beef prepared from two forequarter muscles

The functionality of pre-rigor beef was investigated in terms of the effects of phosphate reduction and curing of hot-boned meat on the processing and sensory properties of relatively low-value muscles, M. infraspinatus (IS) and M. pectoralis profundus (PP), from the forequarter. Muscles were excised within 90 min post-mortem (HB) or, from chilled carcasses, 24 h post-mortem (CB), and were injected to 115% of green weight with brine containing phosphate and were vacuum tumbled continuously for 2 h. Hot-boning gave lower total yield of cooked meat for both muscles. Hot-boned PP joints had slightly higher (P<0.05) cook loss than cold-boned. Reduction of added phosphate (from sodium tri-polyphosphate) from 0.3% to 0.15% of cured meat had detrimental effects on colour; joints containing the conventional 0.3% were lighter (P<0.001) and redder for both muscles. Hot-boning gave PP joints which were rated less tender by sensory panels, corresponding with higher (P<0.001) hardness TPA values, higher (P<0.05) Warner-Bratzler shear force (WBSF) values and shorter (P<0.05) sarcomere lengths. Effects of phosphate level and boning method were less in IS joints. In these, hot-boning gave products that were rated by sensory panel as slightly more tender but there was no effect on TPA or WBSF values. Furthermore, total yields from hot-boned products did not reflect the expected increase in functionality and reducing added phosphate during processing had a detrimental effect in binding and forming of joints.

사후 저장온도가 온도체 발골 육계 가슴육의 이화학적 특성에 미치는 영향

The objective of this study was to examine the effects of high and low chilling temperature on the water-holding capacity (WHC) and tenderness of hot-boned breast meat of broiler chickens. Breast meat was obtained from 32 broiler chickens within 15 min post-mortem (PM), and then divided into two groups. One group was chilled at <TEX>$-1^{\circ}C$</TEX> and the other group was stored at <TEX>$30^{\circ}C$</TEX> for 3 hr, and then all the samples were chilled at <TEX>$2^{\circ}C$</TEX> until 24 hr PM. During the storage, their physicochemical characteristics were tested at 15 min, 3 hr and 24 hr PM. These included pH, R-values, cooking losses, sarcomere length, MFI, and shear force of the breast meat, none of which was different (p>0.05) between the two temperature treatments at <TEX>$-1^{\circ}C$</TEX> and <TEX>$30^{\circ}C$</TEX>. However, sarcomere length was shortened more at <TEX>$-1^{\circ}C$</TEX> than at <TEX>$30^{\circ}C$</TEX>, MFI was larger at <TEX>$30^{\circ}C$</TEX> than at <TEX>$-1^{\circ}C$</TEX>, drip loss was greater at <TEX>$30^{\circ}C$</TEX> than at <TEX>$-1^{\circ}C$</TEX>, and WHC was lower at <TEX>$30^{\circ}C$</TEX> than at <TEX>$-1^{\circ}C$</TEX>(p<0.05). In brief, in terms of yield and tenderness, broiler breast meat stored at <TEX>$-1^{\circ}C$</TEX> was superior to that stored at <TEX>$30^{\circ}C$</TEX>.

Variations in metabolite contents and protein denaturation of the longissimus dorsi muscle in various porcine quality classifications and metabolic rates

The purpose of the present study was to investigate the variations in metabolite contents and muscle protein denaturation in various porcine quality classifications and metabolic rates. A total of 226 crossbred pigs were evaluated. Samples were classified based on muscle pH 45 min and R-value into fast or normal glycolysing group. Drip loss and lightness ( L*) were used to assign samples as PSE, RSE, or RFN pork. Normal-glycolysing PSE pork contained an exceptional amount of initial glycogen and the high level of lactate at 24 h postmortem (PM). The initial levels of metabolites related closely with muscle pH, R-value and protein solubility at 45 min PM. The fast glycolysing group exhibited severe protein denaturation during the early postmortem period, and among them, fast-glycolysing PSE pork exhibited most pronounced protein denaturation. Via examination of each sarcoplasmic protein fraction, it was found that the bands for fructose-6-phosphate kinase, creatine kinase, triosephosphate isomerase, and myokinase were generally more evident as fainter bands in the fast-glycolysing pigs.

Effect of genotype and seasonality on pig carcass and meat characteristics

The effect of the genetics and the slaughter time on pig carcasses and raw ham characteristics has been assessed. With this aim, 1257 pigs from five different crosses including Duroc (DU), Landrace (LR) and Large White (LW) in five slaughters distributed along a year (namely, December 2000, March, April, July and November 2001) were used for the study. The variables studied included carcass weight (CW), ham weight (HW), lean meat percentage in the ham (% Lean), pH at 45 min post-mortem (pH 45 min) and at 48 h post-mortem (pH 48 h). The percent of ham yield (% HW–CW ratio) was calculated as the ratio ham weight/carcass weight multiplied by 100. Semimembranosus muscle (SM) from 237 hams was collected at 48 h post-mortem in order to determine the moisture, protein and intramuscular fat content and pH measurement in the laboratory (pH Lab). A univariate analysis of variance including genetics as fixed factor and slaughter time as random factor revealed that carcass and meat traits are influenced by both the time of year in which the animals are slaughtered and the genetics; however, the latter exerts a less significant effect than the slaughter time.

Turkey Carcass Chilling and Protein Denaturation in the Development of Pale, Soft, and Exudative Meat

Pale, soft, and exudative (PSE) meat is a growing problem in the turkey industry and has been associated with processing conditions such as slow carcass chilling. The development of PSE meat is caused by protein denaturation resulting from a rapid rate of pH decline early postmortem (PM) while carcass temperatures are still elevated. This research was conducted to determine the relationship of slow chilling to protein denaturation and PSE development. A total of 48 toms were conventionally processed in 2 trials at 22.5 wk of age, and chilled at 0, 10, 20, or 30°C for either 45 or 90 min before deboning (at 60 or 105 min PM). Temperature and pH of the breast muscle was recorded at 15 min PM, at the time of deboning (60 or 90 min PM), and at 24 h PM. Color was determined at deboning and again at 24 h PM. Gel strength, cook loss, expressible moisture, total protein solubility, and bound phosphorylase quantities were determined on the fillets at 24 h PM. There was no difference in carcass temperature at 15 min PM, but by 105 min PM each temperature treatment was significantly different, with the carcasses chilled at 0 and 10°C having the lowest temperature, the 30°C-chilled birds having the highest temperature, and the 20°C-chilled carcasses being intermediate but significantly different from either extreme. The carcass temperature differences at 105 min PM indicated that the carcass experienced differing chilling rates. To varying degrees, slower rates of chilling resulted in lower pH, greater degree of lightness (L* value), greater cook loss, and reduced gel strength. However, chilling rate had no effect on total protein solubility or myofibrillar phosphorylase for any of the treatments. Chilling rate seems to contribute to PSE turkey meat characteristics but by a mechanism independent of total protein solubility or myofibrillar phosphorylase.

The role of carcass chilling rate in the development of pale, exudative turkey pectoralis

Pale, soft, and exudative meat is a growing problem in the turkey industry that has been associated with processing conditions such as improper chilling. This condition is caused by accelerated postmortem glycolysis while carcass temperatures are still elevated, resulting in protein denaturation and poor meat quality. To evaluate the involvement of chilling rate, 48 toms were conventionally processed at 17.5 wk of age and chilled at 0,10, 20, or 30 C for 45 or 90 min and deboned. Temperature and pH of the breast fillet were recorded at 15 min, deboning time, and at 24 h postmortem (PM). Drip loss, L* value, expressible moisture, gel strength, and cook loss were determined on the fillets at 24 h PM. At 15 min PM, there were no temperature differences among treatments. At deboning, the carcasses chilled at 30 C had the highest fillet temperature and had significantly lower pH values when compared to those chilled at 0 and 10 C. L* value was significantly higher in carcasses chilled at 30 C and deboned at 60 min PM when compared to 0 and 10 C chilled carcasses. There were no significant differences in L* values at 105 min and 24 h PM among any treatment group. Drip loss and cook loss were significantly higher in carcasses chilled at 30 C compared to the remaining treatments. There were no differences in expressible moisture at 60 or 105 min PM or gel strength at 60 min PM in any of the treatments. However, at 105 min PM, carcasses chiled at 0 C had higher gel strength when compared to the remaining treatments. These results indicate that there is a relationship between chilling rates and meat quality with slower chilling producing PSE-like characteristics.

The effect of time and type of electrical stimulation on the calpain system and meat tenderness in beef longissimus dorsi muscle

Effects of type and time of electrical stimulation on the calpain system, sensory and objective meat quality in the M. longissimus thoracis et lumborum from 38 pasture-fed carcasses, were investigated under conventional chilling conditions. High voltage stimulation was applied to whole carcasses at 3 min post-mortem (pm) and to sides at either 40 or 60 min pm, whilst low voltage stimulation was applied to whole carcasses at 3 min pm and to sides at 40 min pm. Unstimulated sides served as controls. The levels of extractable μ-calpain and calpastatin decreased during stimulation by 28–44% and 8–17%, respectively. Shear force and adjusted tenderness score showed that stimulation at 3 min, irrespective of type of stimulation, resulted in significantly tougher meat ( P<0.05) which was associated with an rapid rate of pH decline, compared to stimulation at 40 min. Higher calpastatin levels soon after stimulation at 3 min ( P < 0.05) and lower μ-calpain level at 24 h pm for high voltage stimulation at 3 min ( P<0.05) coincided with the tougher meat. On the other hand, high voltage stimulation at 40 and 60 min resulted in similar tenderness and levels of μ-calpain and calpastatin post-stimulation and 24 h pm. Significantly tougher meat from the control sides, with a higher μ-calpain levels at 24 h pm and similar sarcomere length, compared to those from low voltage stimulation at 40 min ( P<0.001), appeared to be linked to the later activation of the calpain system. Results from the current study suggest that early application of stimulation may be associated with a very rapid decline in pH and consequently a reduction in meat quality.

Relationship between early post-mortem muscle pH and shortening-induced toughness in the Pectoralis major muscle of processed broilers air-chilled at 0°C and ‐12°C

1. An experiment was conducted to investigate the development of shortening-induced toughness in the Pectoralis major (PM) muscles of commercially processed broilers, air-chilled at 0°C and ‐12°C, as a function of muscle pH early post-mortem. Electrical stimulation was used immediately after stunning and neck cutting to provide carcases with pH values 15 min post-mortem (pH 15 min ) ranging between 6.79 and 5.85. 2. The deep PM muscle temperatures of carcases chilled at ‐12°C were lower (cooler) after primary chilling and at 215 min post-mortem than those chilled at 0°C, although chilling regimen had no major effect on pH values over the 24 h post-mortem period. However, carcases chilled at ‐12°C had longer sarcomeres, lower cooking losses and lower shear force values than those chilled at 0°C. 3. Correlation analysis of the results for both chilling regimens clearly demonstrated that over the pH 15 min range 6.79 to 5.85, carcases with the lowest pH 15 min values had the shortest sarcomeres, the highest cooking losses and the toughest meat. In addition, there was no evidence to support the occurrence of cold shortening within this population. This suggests that an early onset of rigor at higher temperatures in broiler carcases, as well as inducing rigor shortening and toughness, might also induce greater protein denaturation and subsequent loss of water holding capacity as manifested in increased cooking losses. 4. Quadratic regression curves showed that over the pH 15 min range 6.80 to 6.30, only the fast chilling regimen at ‐12°C could inhibit rigor shortening and minimise changes in cooking loss and shear force values. However, neither chilling regimen was effective in preventing severe rigor shortening, increased cooking losses and adverse toughness in carcases with pH 15 min values below 6.30. 5. The benefits of fast chilling carcases with pH 15 min values above 6.3 can also be quantified in terms of carcases exceeding a 4.00 kg/cm2 toughness threshold. Only 1.9% of these carcases chilled at ‐12°C exceeded this limit (maximum shear force value of 4.72 kg/cm2) compared to 34.9% of the carcases chilled at 0°C (maximum shear force value of 8.46 kg/cm2), further emphasising the considerable reduction in textural variability and improvement in tenderness gained by fast air-chilling at ‐12°C.

Post-mortem variation in pH, temperature, and colour profiles of veal carcasses in relation to breed, blood haemoglobin content, and carcass characteristics

A total of 1764 male calves of the Meuse–Rhine–Yssel (MRY) and Friesian–Holstein (FH) breeds were slaughtered at two commercial slaughterhouses to investigate the variation in pH, temperature, and colour of Dutch veal carcasses processed without electrical stimulation and with a moderate chilling regimen (average temperature of the longissimus lumborum muscle at 45 min, 3, 24, and 48 h post-mortem was 38.4, 23.3, 3.7 and 1.9°C, respectively). Blood haemoglobin content was determined 2 weeks before slaughter. The efficacy of captive bolt stunning was scored and the carcass movements after shackling registered. Temperature and pH measurements were carried out at 45 min, and 3, 24, and 48 h after slaughter in the longissimus lumborum muscle (LL). Muscle surface colour (CieLAB-values) was measured with a colorimeter at the rectus abdominis muscle at the same times post-mortem. Carcass conformation and visual carcass colour classification were determined at 45 min post-mortem. Carcasses with a better EUROP-conformation score and heavier weight showed a higher rate of pH decline and a slower cooling rate. Slight differences in cooling systems between the slaughterhouses caused marked differences in pH and temperature profiles. Significant differences in carcass weight were observed between the MRY and FH breeds, leading to significant differences in pH and temperature profiles. Carcass colour of the two breeds was similar. Veal carcass colour in general was not related to the observed variation in post-mortem pH and temperature in the longissimus lumborum muscle and was shown to be more associated with the blood haemoglobin content. Haemoglobin content of the blood in the period before slaughter was shown to be related to the visually assessed carcass colour at 45 min post-mortem (using a 10-colour scale), as well as to the instrumentally determined L*-value, with significant correlation coefficients of 0.61 and −0.61, respectively. Repeated captive bolt stunning to obtain unconsciousness significantly decreased pH at 3 h post-mortem. The degree of carcass movement after slaughter did not influence pH, temperature, or colour profiles of the carcasses.

Rapid post-mortem glycolysis and delay chilling of turkey carcasses cause alterations to protein extractability and degradation of breast muscle proteins.

SDS-PAGE banding patterns of myofibrillar protein samples from turkey breast muscle with pH < or =5.8 at 15 min post-mortem (rapid glycolyzing) contained 133, 142, and 165 kDa bands that were absent in samples from carcasses with pH >6.0 at 15 min post-mortem (normal glycolyzing). These extra protein bands contained fragments of myosin as identified by Western blot analysis. Myosin fragments were also observed in protein samples from breast muscle not allowed to cool until 110 min post-mortem (delay chilled). In addition to myosin degradation, neublin degradation was more extensive in samples from rapid glycolyzing carcasses than for normal controls. Creatine kinase and glycogen phosphorylase were present in myofibrillar protein extracts of rapid glycolyzing carcasses in higher quantities than in normal controls. Results of this study provide insight into the molecular basis for previously reported reductions in meat quality of rapid glycolyzing and delay chilled turkey meat.

Influence of preslaughter stunning on turkey breast muscle quality

Pectoralis muscle quality was evaluated from 18-wk-old tom turkeys after electrical stun, carbon dioxide stun, or no stun methods were applied. Color was measured on raw muscle and cooked meat using a colorimeter. Muscle pH was measured 15 min post-mortem (initial), 24 h post-mortem (final), and after cooking. The right Pectoralis muscle of each carcass was excised for m-calpain analysis within 4 min post-mortem. After 24 h of storage at 4 C, the left Pectoralis muscle was excised to determine cook loss and shear force measurements. No significant difference was found in initial muscle pH (15 min) from turkeys receiving electrical or carbon dioxide stunning, 6.36+/-0.15 and 6.20+/-0.14, respectively. However, initial muscle pH for birds that were not stunned (5.99+/-0.08) was lower (P < 0.05) than the muscle pH of birds stunned using either of the two stunning methods. Stunning method had no effect on the final muscle pH, raw muscle color, cooked meat pH, cooked meat color, cook loss, or shear force. Cook loss was found to positively correlate with initial muscle lightness (r = 0.53), and cooked meat lightness (r = 0.48), but to negatively correlate with cooked meat yellowness (r = -0.48) and shear strength (r = -0.43). m-Calpain activity declined with the stunning methods in the following order: electrical > carbon dioxide > no stun. In addition, m-calpain activity was found to correlate with initial muscle pH (r = 0.95) and with cooked meat shear force (r = -0.43). The results of this study show that electrical stunning, carbon dioxide stunning, and no stunning methods provide comparable cooked turkey breast meat quality with no consistent differences after aging on the carcass for 24 h.